With the development of electronics technology in recent years, the reduction in size and the increase in capacitance have been rapidly advanced on laminated ceramic capacitors. Further, with the reduction in size and increase in capacitance for laminated ceramic capacitors, dielectric ceramic layers have been also progressively reduced in thickness, and the development of laminated ceramic capacitors including dielectric ceramic layers of 1 μm or less in thickness has been also actively carried out.
Due to the fact that the dielectric ceramic layers reduced in thickness increases the electric field applied to the dielectric ceramic layers, and it is important to ensure reliability under high-temperature load. Moreover, the applied electric field is increased more and more with the reduction in thickness for the dielectric ceramic layers, and it is thus becoming hard to achieve desired high reliability.
As an approach for improving the reliability of laminated ceramic capacitors, it has been conventionally common to add a rare-earth element such as Y, Dy, Ho, and Gd, which has the effect of suppressing the movements of oxygen vacancies, to a BaTiO3 based composition as a main constituent, while it is important to control crystal triple points and heterogeneous-phases (segregation phases) in order to address the reduction in thickness for dielectric ceramic layers.
For example, Patent Document 1 proposes a dielectric ceramic including: main crystal grains composed of a perovskite-type composite oxide containing Ba, Ti, a rare-earth element, Mg, and Mn as metal elements; and an interfacial grain boundary phase and a triple-point grain boundary phase formed by the main crystal grains, where a crystalline phase composed of Ca4Y6O(SiO4)6 is present in the triple-point grain boundary phase.
In the case of Patent Document 1, in the formation of the dielectric ceramic, the formation of a crystalline phase composed of Ca4Y6O(SiO4)6 within the dielectric ceramic, in particular, at the crystal triple point which easily discharges and undergoes a significant decrease in dielectric breakdown voltage can increase the insulation property of the crystal triple point, thereby improve temperature characteristics of electrostatic capacitance even when dielectric layers are reduced in thickness, and makes it possible to improve the high-temperature load life.
Patent Document 1: Japanese Patent No. 4480367 (claims 1, 2, and 5; paragraph [0020])